The present invention relates to a three-dimensional (3D) display device capable of allowing viewers viewing 3D images without wearing any special glasses and particularly a 3D display device that employs horizontal and parallel strip light sources, an image forming device, a horizontal parallax barrier, and a transmissive light modulation panel to form images on the left and right eyes of viewers for the viewers to see 3D images.
Presently, developments of 3D display devices are heavily focusing on the function and features such as high resolution, low ghost images, multiple viewing zones and viewing without using special glasses. The naked-eye type 3D display devices which include vertical parallax barriers now commercially available can display pictures with low ghost images. However they do not have smooth multiple viewers tracking function.
FIG. 1 illustrates a 3D display method which adapts a conventional technique. On the LCD device 1, there is a vertical parallax barrier 21 to separate the images of the left eye and right eye to achieve the 3D effect. The parallax barrier 21 matches the pixel pitch of the LCD device 1 to allow viewers to see two separated images from two eyes at a selected distance. Whereas, viewers have to fix the eyes to a correct position to see the correct 3D images. Otherwise viewers"" two eyes will perceive ghost images or reversed stereo images. If an eye tracking device is coupled to the display device, when the images are reversed, the images on the two eyes may be switched, then viewers may still see the correct 3D images. However when viewers"" eyes are between the correct and the reverse-stereo positions, the image crosstalk between the two eyes will still happen. U.S. Pat. No. 6,049,424 discloses a technique which uses liquid crystal to change the shape and position of the parallax barrier. But the resolution of the parallax barrier formed by liquid crystal is limited. It also cannot achieve smooth tracking effect. And the offering tracking function is applicable only to a viewer.
Taiwan Patent No. 381394 discloses a smooth tracking naked-eye 3D display device which uses a horizontal micro-retarder to couple polarization changes of a light source to offer tracking for multiple viewers. However the retarder material functions differently to light of different wavelengths. It tends to generate ghost images between the images on two eyes. Moreover, the machining of the micro-retarder forms a transition area between different areas of different retardation states which induces crosstalk and in turn causes ghost images.
The primary object of the present invention is to resolve the foregoing disadvantages. The invention provides a parallax barrier type autostereoscopic display device which allows viewers being smoothly tracked when viewing.
Another object of the invention is to provide a parallax barrier type autostereoscopic display device that is capable of performing tracking for multiple viewers.
A further object of the invention is to provide a parallax barrier type autostereoscopic display device that is capable of reducing ghost images.
To attain the foregoing objects, the invention consists of a light source which is composed of one or more pairs of horizontal and parallel strip light sources, an image forming device located in front of the light source, a transmissive light modulation panel disposed at a selected location at one side of the image forming device opposite to the light source, and a horizontal parallax barrier located between the image forming device and the transmissive light modulation panel. The device thus constructed allows multiple viewers being smoothly tracked during viewing and can also reduce ghost images.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.